Acceptance of electro-acoustic impulses seems to characterize much of the more interesting 21st Century European improvised music. Yet like the best sounds produced by influence-accepting free music, its hoary half-brother, electro-acoustic improv is most absorbing when its a hybrid. Too acoustic and it lacks the futuristic sounds of electronics; too electronic and it becomes an exercise in science or physics, not art.

Which is what makes these two CDs —recorded oddly enough in the same month — praiseworthy. The performers have mated wiring and treatments with real time acoustic instruments. In each case the output yields its own logic and soon takes over your inner ear to such an extent that you begin to forget the passage of time. From France comes pianist Sophie Agnel, improvising for a little more than 58 minutes among the tapes and electronics of musique concrète composers Lionel Marchetti and Jérôme Noetinger. While the turntables of Austrian dieb 13 (Dieter Kovacic) are meshed with the prepared percussion and treatments of Swiss-German drummer Günter Müller and American expatriate Jason Kahn for slightly more than 39½ minutes on the other disc.

Agnel, who got her start playing jazz and classical music, before turning to free improv with the likes of hurdy gurdyist Dominique Regef, guitarist Noël Akchoté and in a duo with fellow experimental pianist Andréa Neumann, is parsimonious in her choice and sounding of notes. Presumably creating inside and outside the box — or at least the piano frame — she never plays a chord where two notes would do or two notes when one would suffice. If a theme is introduced, its quickly subsumed beneath the crinkle and tinkle of electronics. Should a glissando appear it dissolves into intermittent buzzes or some Donald Duck-style quacks. Strumming and scratching strings inside the frame is sometimes used as well, but never for more than a few seconds.

Outside of the occasional shaded right handed treble tremolos, in fact, the only time the piano really stands out from the mix is when Agnel indulges herself by bearing down on the sustain pedal for a protracted interval. This CD after all, is a mixture of red, gray and noise (!) — to translate the title — which takes it silence as seriously as its clamor. Two of the tracks at 33 and 10 seconds respectively are nothing but noiselessness.

Between themselves, Marchetti who teaches at Université de Lyon and his long-time partner Noetinger, who is also a member of the 12-member electronics aggregation MIMEO (Music in Movement Electronic Orchestra) unquestionably make up for the silence. During the course of the piece, panoply of found and otherworldly sounds makes their appearance. Many times, the crinkle, tinkle and overall rumbles of the tapes and electronics broken by what could be sonar responses to the whirrs and bangs of setting up a space antenna or monitoring short wave broadcasts from the Mother Ship. Elsewhere will be something that appears to be a mechanical raspberry, a sequence of fowl noises (sic), a harmonica tone, a penny whistle, spinning tops and a bowling ball hitting the pins. The last brings out a pastoral semi-classical melody from Agnel. Bombs appear to be falling, video game players seem to be nosily racking up points and a crackling fire dissolves what could have been a human voice.

Although only nonsense syllables are audible when a voice shouts through a megaphone early in the proceedings, by Après-midi an English voice clearly repeats youll get the message. Repeats that is, until the scratch of metal on metal and piano tinkles buries the phrase within the background of what could be the bark of a mechanical dog. Constantly reoccurring keyboard notes presage the end with what are apparently the dying cranks of a machine finally winding down.

Dream-like mechanical buzzes and tones drive the second disc, which could never be mistaken for earlier percussion extravaganzas like (Buddy) RICH VS (Max) ROACH or Art Blakeys ORGY IN RHYTHM. Despite the personnel, this is probably the quietest session involving two drummers ever made.

With a steadfast, regular pulse, unlike the ur-modernist aspirations of the preceding trio, many times the session appears to be the soundtrack for a trans-continental journey by fast train, with the louder outpourings reminding the listener of rail cars streaking past a level crossing. Every tonal shade must be carefully scrutinized though, so that the constant repetitive car crossing stays mesmerizing and not sleep inducing.

The three musicians are definitely set up to make the trip as pleasing and transparent as possible. For the past 20 years Müller has played a unique kit whose mobile pick-up and microphone system allows hand-generated percussion sounds to be modulated electronically. He has been associated with a raft of electro-acoustians, the best known of which is the POIRE_Z quartet. Another reformed percussionist, now domiciled in Zürich, Kahn has lived in Europe since 1990 and now uses the computer and live sampling software to amplify his kit. His playing situations have ranged from a duo with no-input mixing board player Toshimaru Nakamura to membership in expatriate American composer Arnold Dreyblatts Orchestra of Excited Strings. Most futuristic of the three, 28-year-old Dieb13, has been has rendering cassette players, vinyl, CDs and computer hard disks into instruments since the late 1980, and most notably has played in such Viennese aggregations as efzeg.

As the journey continues the tape machine hums and turntable rumbles begin to sound more transportation oriented. Almost every impulse could be the click of rail cars passing over the tracks, with the constant ringing of the train bell subsuming other sounds. Slowly moving in and out like the tide, the thumps, clatters, bangs and scratches meld together, with one composition melting into the next.

Is that the rumble of a motor you hear at one point or the buzzes and whistle of a locomotive, you wonder? Is that the crackle and sizzle of electronics slowing advancing or is it a video game in use in the lounge? And are those distinctive tempered scrapes arising initially from a gamelan or a vibraharp sample or is the tempered metal of a railroad tie adhering to the rail? At times it appears as if frog sounds or birdcalls have been adapted for the journey, while the few times a voice is heard, memories of air traffic control conversation intrude into the land-locked journey.

Noise, streaming, clatter — each of these discs provide soundtracks for an overactive imagination as well as a way to shake up your thought process. Singly or together, theyre worth investigating.